Selective Electroreduction\nof CO<sub>2</sub> to Ethanol\nvia Cobalt–Copper Tandem Catalysts

The selective electrocatalytic conversion of CO<sub>2</sub> into\nmulticarbon products, such as ethanol, is a major technological challenge.\nCurrently, this reactivity is limited by the sluggish formation of\nC–C bonds inherent to many single-site catalysts. Here, we\nreport a new tandem electrocatalyst based on earth-abundant elements,\nwhich facilitates the selective CO<sub>2</sub>-to-ethanol conversion.\nThe composite catalyst consists of neighboring cobalt and copper atoms\nanchored to electrically conductive nitrogen-doped carbon. At low\noverpotentials (<i>E</i> = −0.8 V vs reversible hydrogen\nelectrode), the system shows high selectivity for ethanol production\n(faradaic efficiencies >70%), while retaining its reactivity and\nstability\nfor 18 h. A CO spillover mechanism is proposed as the basis for the\nobserved selectivity, where efficient CO generation at Co sites leads\nto high local CO concentrations at neighboring Cu sites, thereby favoring\nC–C coupling and ethanol formation. Operando X-ray absorption\nspectroscopy reveals a dynamic transformation of the single-site Cu\ninto Cu clusters as actual active sites. <i>In situ</i> infrared\nspectroscopy reveals the formation of intermediate CO at Co sites,\nwhich undergo subsequent spillover and C–C coupling on the\nCu clusters. This design concept offers new avenues for noble metal-free\ntandem electrocatalysts for the conversion of CO<sub>2</sub>-to-multicarbon\nproducts.